Successfully developed special rolls for finishing rolling of wire rod (ordinary wire) rolling mills
For the finishing rolls of Ø6.5-Ø8mm wire rod (referred to as ordinary wire) rolling mills with a rolling line speed of less than 25 m/s, medium alloy infinite chilled centrifugal composite rolls were used in the past, not only the single-slot steel passing rate is low, but also the surface of the wire rod The quality is also subpar. After continuous experimentation and continuous improvement, the company finally successfully developed a special roll for finishing rolling on the common rolling line-medium alloy chilled centrifugal composite roll (the code name of this new material roll is L3A). The medium alloy chilled centrifugal compound roll and the medium alloy infinite chilled centrifugal compound roll, under the condition that the alloy content and price are basically the same, due to the careful design of the chemical composition and the bold improvement of the technical control method of smelting and pouring, the medium alloy chilled centrifugal compound roll The working layer of the roll has obtained the structure of sorbite + bainite + martensite, and the working layer only contains a small amount of graphite in the pure white layer, and the hardness of the roll body is as high as 75-78HSD. Due to the above-mentioned advantages of the medium alloy chilled centrifugal composite roll, not only the wear resistance of the roll is significantly improved (30-40% higher than the original), but the surface quality of the wire rod is also significantly improved. This new material roll has been widely used in the finishing K1 stand of ordinary rolling mills, and has won high praise from users. At the same time, it has also been successfully promoted and applied to the rolling of Ø10-Ø12mm round steel finish rolling K1 rolls, and has also achieved good results.
Successfully developed centrifugal rolls for intermediate rolling in bar (wire) mills
In the bar (wire) rolling mill, the rolling group rolls are second only to the roughing group in terms of reduction. The middle roll requires higher roll strength and should have certain wear resistance. Therefore, the middle nickel ball roll cast by the conventional method has been used in the past. The medium-nickel ball roll cast by the conventional method not only has high cost, but also has a relatively low tensile strength, and the resulting roll breakage often occurs. After market research, it is considered that the pouring method of the roll must be changed in order to further improve the internal quality of the middle roll and reduce the cost. After comparative analysis, it is considered that the production of middle rolls by centrifugal casting method is more advanced. The outer layer (working layer) of the centrifugal roll is made of medium-nickel infinite chilled cast iron, and the inner layer is high-strength ductile iron. For this reason, the technicians of Zhongqiang Rolling Co., Ltd., after repeated tests and continuous improvement, finally found the chemical composition and roll body hardness that meet the requirements of the working layer of the Zhongqiang centrifugal roll. Centrifugal rolls for rolling mills in rod (wire) mills were successfully developed and mass-produced.
In the medium rolling mill, the medium nickel centrifugal roll was used to replace the medium nickel ball conventional roll successfully. First of all, the strength of the center of the roll is greatly improved, basically eliminating the problem of roll breakage. The average tensile strength of medium nickel centrifugal rolls is 599N/mm2, while the average tensile strength of medium nickel ball conventional rolls is 449 N/mm2. Secondly, the cost of rolls has dropped significantly. According to statistics, the production cost of medium nickel centrifugal rollers was 2489.90 yuan/t lower than that of medium nickel ball conventional rollers (the cost decreased by 32.63%), and the annual cost reduction was 4.35 million yuan, with remarkable economic benefits.
Independent research and development of centrifugal rolls for channel steel finishing rolling
The rolls used for the finish rolling of channel steel have long been casted in the normal way, with medium-nickel-chromium-molybdenum-molybdenum nodular infinite chilled rolls (referred to as medium-nickel chilled ball rolls). The groove of the channel steel finish roll is deep. When the conventional method is used for pouring, due to the large hardness drop of the roll body and the low hardness of the groove bottom, the wear resistance of the roll is poor, which cannot meet the requirements of use. The surface quality of the channel steel is also poor. For the nickel chilled ball roll in the conventional method, because it is formed by one-time casting, the internal and external materials are the same, so it is difficult to take into account the strength of the core of the roll and the wear resistance of the roll body at the same time. Often in order to improve the hardness and wear resistance of the roll, the strength of the roll is It will drop and cause broken rolls, on the contrary, the rolls are not wear-resistant. This technical problem has not been solved well for quite a long time. In order to solve this difficult problem, some people have attempted to cast grooved rolls, and the wear resistance of cast grooved rolls can be significantly improved. But its cold profile design of cast channel steel grooved roll is very complicated to manufacture, and the work of cold profile closing before pouring and removing parallel iron after casting is very troublesome again. At the same time, the material selection for casting groove rolls is also a big problem: when using medium-nickel infinite chill rolls, the rolls are easy to break due to the low strength of the rolls (бb150-180N/mm2); when using medium-nickel chilled ball rolls, the strength of the rolls It is better, but the slot hole of the casting roll will have a positive and negative surface (a surface that looks like inclusions will appear on one side), so it cannot be used. Therefore, the popularization and application of casting groove rolls on the channel steel finishing stand has not been successful. Because the technical problem of the channel steel finishing roll has not been solved for a long time, the nickel cold ball roll in the conventional casting method has always been used.
After discussion by scientific researchers, it is considered that the centrifugal casting method is used to produce channel steel finish rolls, which is relatively easy to meet the technical requirements of channel steel finish rolls. The centrifugal roll adopts secondary casting, the outer layer is alloy ductile iron, and the inner layer is high-strength ductile iron, which can well solve the core strength and the hardness and wear resistance of the outer layer. The above centrifugal rolls have been actually used by Shandong Zhangqiu Honghui Sectional Steel Manufacturing Co., Ltd. for rolling 8# channel steel with a single channel. . It has been identified that the development of centrifugal rolls for channel steel finishing has been successfully developed.
